"Link plz "

https://www.google.com/patents/US2677855

Look close at the 2 pictures and note that gaps of .003 are used!!!.....far cry from today for sure. Also note the patent write-up " molding a distributor cap so that the track for the rotary distributor arm will be accurately and precisely positioned with respect to the distributor segments or contacts to thereby give the precise clearance between the distributor arm and contact segments without any need for machining either the track or the segments"
Also " contacts and the rotary distributor arm should be maintained within a close tolerance, for example, .001 inch to .003 inch."


Those gaps are 1/50 of some measured in our testing!

Also think back to the Bluestreak cap test done where the terminals did not extend down to the rotor tip.......actually they were arcing upward which sounds familiar to the above patent.....except Bluestreak rotor didn't make it all the way to the terminals!!!

Also Note the patent owner was Mallory.......any chance they were grabbing up any idea and locking it up in a patent if possible?

Based our small sample size testing the secondary high voltage is significantly lowered by decreasing the huge gap by secondary machining.....even crude secondary machining. So why go for the gold when silver will do just fine (compared to what is there for secondary voltage)?

Is there any chance the manufacturer's actually want large secondary voltage so they can sell more ignition parts....?......you would have to be a manufacturer to know that to be true or not.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

That's really interesting. Mallory made exceptionally fine ignition components at that time. I don't know if they ever used this method or if it's one of those probably-excellent ideas that never got commercialised. You've got a good point: a cap/rotor setup with ~0.002" gaps would give excellent service for many, many years, thus gutting the replacement-part market.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Detailed instructions* to Fit FD117 Tipped Rotor To Cap assume you have no jig or feeler gauges:

http://tinyurl.com/Fit-FD117-Rotor-To-Cap

Cap was machined in less than an hour.

After using these instructions on Echlin Cap #2 that had .038 gaps & .014 eccentricity (with the long MO3000 rotor) the final product was checked out on a jig with feeler gauges to see how well the process worked.......the results were gaps varying between .015 and .022 with eccentricity of less than .003.

Next up.......testing secondary voltage results......expect warm enough temps here to meet testing conditions mid week. Hopefully the results will be voltages around 2000 so that a crude cap machining effort matched to a long wide rotor tip is good enough for most to beat today's cap and rotors by a wide margin.

* warning again......always insure the cap is correctly oriented on the distributor when testing and/or using the machining process.....make sure the tang at the vacuum advance unit is engaged in the distributor cap slot.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Below Summary contains FD117 Rotor Tip Secondary Volt (SV) Test added to all previously posted data.

The FD117 Wide Rotor tip on MO3000 rotor base was fitted to the cap with .022 gaps and had the best SV reading obtained so far.....1400 Volts.

Additionally another test was done spreading the spark plug gap to .045 and the SV results were .....2900 volts.

Note that the posted HEI Sun testing done almost a decade ago showed the SV doubled at that time from 5000 to 10000 when the plug gap was opened up to .045".

In reading over the Summary and deciding what action you might take consider the following:
1) Using a current day stock aftermarket cap and short rotor is likely exposing the engine ignition system to SV above 20,000 volts .....likely stressing ignition components to a noticeable shorter lifetime & impacting spark at the cylinders.
2) Using a current day stock aftermarket cap and long rotor has a high probability of a cap and rotor hit raising the potential for stripping a distributor gear....best to check clearance on a spare distributor before using(do not forget to apply a side load to the gear).
3) Using a current day stock aftermarket cap, regardless of brand, is likely to have significant eccentricities of the cap terminals contributing to the above hit potential
4)60's Double wide terminals with smaller gaps than today put SV significantly lower than any current day cap rotor combo based on the 19 tested so far
5)Simple machining of a current day rotor and cap as outlined in the Summary can bring SV down to levels even lower than the 60's setup.

The Summary:

http://tinyurl.com/RotorDistributorGapSummary

On to...... reliability testing to see how the ignition components do with the low SV 2900 volts (with plug gaps set at .045").

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

One question: are these secondary voltage measurements being made with the engine running, or with a spark plug in open air, or by another method?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

"One question: are these secondary voltage measurements being made with the engine running, or with a spark plug in open air, or by another method?"

SV measured at center of coil wire with engine at temp running at 800 to 900 rpm with air fuel ratio running at 13/1. This has been a constant for all tests.

Meter used allows for measuring by reaching around the wire so there is no need to take the coil wire off at it's connection which might influence the results.

Measurements include the max. and min. SV recorded over the time period. About 5 time periods used and the max reading most frequently displayed is posted. Minimums usually run 500 Volts less than the maximum. So as an example min of 2200 might be accompanied by max of 2900.

Expectation is that the different length of downstream spark plug wires tend to swing the results with the 500 Volt swing likely reflecting those downstream influences?

Absolute SV value is not as important perhaps as the relative value for each case tested. Thus the summary discusses changes by a factor such as 10 to 1.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Below FD117 Rotor Tip On Short Rotor answers the question about whether some short rotors can be extended & have a triple wide FD117 rotor tip which will meet the needed gap requirements.

Pictures showing Blue Streak rotor being modified:
https://tinyurl.com/FD117OnShortRotor

Writeup on limitations of doing the conversion:
https://tinyurl.com/WriteupOnFD117ForShortRotor

End result was not quite as good as putting the FD117 Tip on a MO3000 Long Rotor. Secondary Voltage Testing when the weather gets decent again.

Will try the modification on a different short rotor....after all must find a good use for the short rotors used for testing!!!

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Surprising results when testing a different slant 6.

The alternate engine was rebuilt within the last 2 years and has HEI as well as .045" plug gaps. The existing distributor cap was an Echlin and the rotor was the extended rotor MO3000

The intent was to first check the Coil Wire Secondary Voltage "as is" and then install a FD117 tipped rotor tip and matched distributor cap for the upgrade and Secondary Voltage comparison.
The expectation was that Secondary Voltage would be above 10,000 volts for typical echlin cap eccentricity and gaps to the MO 3000 rotor.

The results for the "as is" rotor and cap were excellent.....1700 volts.
Essentially this cap and rotor were good to go "as is".....a pleasant surprise and well received by the owner.* Obvious once and awhile a decent cap and rotor are made.

Of course someday I'll get the cap and rotor into my jig and check out how good they were machined. I gave the owner the extended triple wide FD117 tip rotors and matched cap to install at a later date to satisfy a future tuneup needs.

* Explained to the owner that at the rpm tested the rotor was likely pointed directly at the cap terminal and that other rpm and vacuum advance settings it would not be......consequently the Secondary Voltage might double at other lead conditions and RPM. Still even a doubling of the Secondary Voltage from 1700 would still be a good place to land.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

FD117 Rotor Building Added Info includes:

1) Different FD117 Rotor Tip Shapes
2) Loose To Hard Rivets
3) Using Various Slant New Rotors As A Base
4) Using Used Slant Rotors As A Base

1) can be summed up in this photo which illustrates some FD117 rotors are only double wide, some have a bulge difficult to work with, and some are 2.5 times wide. Don't go by the picture alone in the ad. Best to make sure the picture of the box is included in the rotor picture to get the feeling the rotor will actually match the picture, The 2.5 times wide rotor tip works best for putting on various slant rotor bases.

http://tinyurl.com/RotorComparison

2) You will find that most if not all FD117 Rotor tip rivets are near impossible to pry out. I resort to putting the portion of the rotor where the rivet is molded to the plastic in a metal vice and squeezing the plastic surrounding the rivet until it fractures. The totally different Slant Rotors typically will allow their rivets to be pried up rather easily. Sometimes they are even loose to begin with with a shaky rotor tip. Once you use super glue when reassembling you might find it near impossible to remove the rivet without destroying the rotor.

3) In the process of attempting to fix every lousy cap and rotor used in my testing I found that just about every rotor can have the FD117 tip put on it. The short tip type Slant rotors must have the FD117 tip installed about 5/64 beyond the short tip location to allow you enough to machine out the cap eccentricities. See the above picture for the various types of rotors.

4) The above rotor fixes were so successful I even tried old used rotors. It was difficult to tell a new rotor from a cleaned & rebuilt old rotor after changing the tip and center electrode.

Anyone skeptical they can pull this off you might want to try a little test of prying out a Slant rotor rivet and see how easy it is for you.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Donpal, this is great stuff. Just for clarification, it looks like you're using "FD-117" as a generic designation to refer generally to these Ford rotors, no matter who makes them or what variety they are. Looking at your new pic, I'm guessing the grey one with the 2.5×-wide rotor tip is a Standard Motor Products № FD-117. The blue one...maybe a United Ignition FR800X? The tan one…maybe an Echlin FA144? Clarity on this point would help people pick up the right Ford rotor to grab the brass contact from.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

FD117 Rotors that were 2.5 width tips came in the following boxes:

http://tinyurl.com/2-5-Wide-Rotor-Came-In-This-Bo

http://tinyurl.com/2-5-wide-rotor-in-this

http://tinyurl.com/2-5-wide-rotor-here-too

The others did not come in a box so I can't tell what to avoid as far as box ID.

I also would not trust going by colors since I did get a blue 2.5 wide rotor and a blue double width rotor.

I do know that what did not come in a box did not match the image that was in the advertisement sometimes....ie the vendor thinks it's alright to give you something that matches the application even though it didn't match the picture posted.

Consequently I trust at this point only buying when I can see the box in the picture with the rotor to improve the odds of getting what you want...not a guarantee but at least an improved chance.

In most cases I purchased the rotors, shipped to the house free, at a total cost between $4 and $5.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

OK. The T-suffix parts from Standard ("Tru-Tech", FD-117T), that's their "value" (cheap) line. Probably bought on a low-bid basis from who knows whom, who knows where (wait, wait, I know, it's a country starting with the letter C). Low quality doesn't matter much for our purposes, I don't guess, because all we're doing is robbing the brass contact from the rotor.

No T-suffix (FD-117) that's Standard's...er...standard line. Generally higher quality than the "T" parts.

There used to be an X-suffix, which was Standard's premium line, but not all parts were available in it and I don't know if there was ever an FD117X.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

_________________
1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

The United Cap Is Challenging To Machine, more so than the other caps, because of two added characteristics:
1) Smaller Terminal Posts
2) Cap Fits Excessively Tight To Distributor Body

In order to insure the Re-Machining Strategy works consistently to decrease the eccentricity and large gaps successfully each cap originally tested is now being re-machined to provide a gap between .020 and .025.

The United Cap proved challenging because of it's small diameter terminal posts which did not provide enough meat to allow a lot of machining. Coupled with a large eccentricity (which meant a significant amount of machining to some posts) the post diameter limited how much of the eccentricity could be removed. Picture a small diameter post width being machined.....as soon as you start cutting beyond the major diameter the post width drastically shrinks in width.

Here is a comparison of OEM post diameters that varied from .31 to .19 inches in diameter:

http://tinyurl.com/kuuygyt

The second problem of "cap fitting too tight to distributor body" effects the eccentricity readings and repeat-ability of gaps each time the cap is installed. I was finding the task of getting repeating gap measurements on the jig to be frustrating with this cap......it would not install in the same location (or tilt in this case) on the distributor. The cap also required to be pried off the distributor once installed using a pry bar (screwdriver).

Although decent readings occurred after a number of attempts and machining efforts this cap would not be the first to reach for in the future for fitting a cap to a rotor. As it was, the best I could obtain was .020 to .030 with extremely narrow final post widths.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

I will add a rotor that i will have a go at using the wide tip off it and installing it onto a MO-3000.
It is a Bosch GB502 , it is for a Chrysler Valiant Hemi 6 distributor .





The I/D is too small to go onto the Slant 6 EI distributor.
Bosch brass stem is 6.26mm and the MO-3000 stem is 6.21mm , so only a mild file to get it to sit in the MO-3000 slot.
Bosch tip is 14.95mm wide.
The hole where the Bosch tip mounts to the rotor is not quite in the same place as the MO-3000 so if using the same mount hole on the tip it would be about 2mm longer than the MO-3000 .
I will let you know how i go .

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DRIVE IT,DON'T HIDE IT